Officials say the fire started just before 4 a.m. at the three-story apartment building on Peralta Street in the East Allegheny neighborhood. Neighbors said they saw flames shooting out of the building, extending out enough to light items on the street on fire.

"This telephone pole was on fire, and there was a couch on the street that was on fire," Iarrapino said. “Flames were coming out of the windows on the first floor.”

At least six people live in the building, and Pittsburgh firefighters say all of them escaped, but one resident did have to go to the hospital for smoke inhalation. Investigators believe the fire started in that person’s apartment.

Firefighters were able to contain the flames to the building even though neighboring homes are only a few feet from its walls.

"With the buildings pressed up against each other, it's very difficult to have access," Deputy Fire Chief Frank Large said. "The access was basically through the front door, where the fire was coming from."

Officials initially had a report that a domestic dispute may have led to the fire, but they now say residents were simply partying and being loud. When one of them went back to his own unit, he passed out on a couch with a space heater nearby. Investigators believe either that space heater or burning cigarettes started the fire.